Rubbing machine



July 10, 1928. A. '3 1,677,112

\ s. F. ANDERSON nuasx ne much-ma 1' I I Original Filed sept.4. 1911'" s sneaks-sheet 1 July 10, 1928. 1,677,112

5. F.IANDERSON RUBBING mourns Original Filed Sept. 4.. 191'! s Shoots-Sheet 2 J NEENTOYR. I j

ATTORNEY.

July 10, 1928. 1,677,112

s. F. ANDERSON RUBBING MACHINE Original Filed Sept. 4, 1917 3 Sheets-Sheet 3 Z y! 2 INZENTOR.

BYQ QWA A TTORNE Y.

Patented July 10, 1928.

UNITED STATES PATENT OFFICE SWAN F. ANDERSON, OF ROCKFORD, ILLINOIS, ASSIGNOR, BY MESI IEAS SIGNMENT S, TO C. PAUL PARKER, TRUSTEE, OFCHIGAGO, ILLINOIS.

RUBBING MACHINE.

Original application filed September 4, 1917, Serial No. 189,563. Divided and this application filed August 4, 1920.

This invention pertaining in general. to portable, pneumatically operated rubbing or polishing machines, is a division of my appl ication, Serial No. 189,563, Patent1,4t9'2,659, blay (i. 1924, and has reference more particularly to the principles of motor construction and operation disclosed in said. application.

The chief object of this invention is to provide a pneumatically operated motor of novel construction for reciprocating a plurality ol rubbing or polishing devices in opposite directions, which motor shall be so embodied inthe frame structure of the inachine as to constitute/n component part of the structure carried by and portable with the rubbing devices. a

One of the primary objects of this invention is to provide in a pneumatic rubbing machine, an organization of pistons, valve mechanism and cooperating parts of such simple, compact and novel construction and arrangement as to obtain most eflicient and economical operation throughout a long period of usage, andto'pern'iit of manufacture I at a comparatively low cost. To this end my invention contemplates, generally stated, the. provision in a rubbing machine of the character in mind, of a pair of parallel laterally spaced pistons, preferably of the double-end type, connected by a device pivoted intermediate and between the ends of the pistons, which device maintains the pistons is to provide an oscillatory valve in co-axial relation with and actuated by said device, thus securing a most direct and compact re lation of parts which function very efliciently for the purpose in mind: and a further object is to provide a lostmotion connection between the valve and said device whereby to control the length of stroke of the pistons.

I have also aimed to provide in combination with a rubbing machine of the character described, an upstanding handle coaxial with the oscillatory valve and removable from the body to permit access to the valve and valve chamber.

Other objects and attendant :nlvantagci- Serial No. 401,232. I V

will be appreciated by those familiar with this art as the inventionbecomes better understood by reference to the following description when considered in connection with the accompanying drawings, in which-- Figure l is a vertical longitudinal sectional view taken centrally through a rubbing machine embodying my invention, with one of the rubbing pads removed from its respective pad holder;

Fig. 2, an end view of the cylinder and slide-inclosing structure, with the end plate removed; i

Fig; 3, a plate;

F igs. 4t and 5, horizontal sectional views taken on the lines 4.4 and 55, respectively of Fig. 1;v

Fig. 6, a cross sectional view through the machine taken substantially on line 66 of Fig.1;

Fig. 7, a similar cross sectional view taken substantially on the line 77 of Fig. 1, with the rubbing pad removed; V

Figs. 8 and 9, detail perspective views of the piston-connecting member and its bridgesupporting member, respectively;

Fig. 10, a vertical sectional View of the osuxillating valve;

Fig. 11, a perspective view in section of one of the pistons;

Fig. 12, a perspective view, of one pad holder slides;

Fig. 13, a perspective view of a guide pin which servesto connectthe slides to the eqiu-ilizing device;

Fig, 1-1. a horizontal sectional view taken substantially along the line 14-14 of Fig. 1.;

Fig. a similar but fragmentary sectional *iew showing the valve moved from neutral to an operative position; and.

face view of the removed end of the qFig. 1G, a horizontal sectional view similar to F 4:, but showing the pistons moved in accordance with the position of the valve showi'r in Fig. 15. i

Fi 17, a perspective view of one of the mean hers slide enclosing structure.

Inasmuch as the present in vention has reference primarily to the principles of motor construction and operation referred to above, it should be understood that these may be employed for reciprocating devices of any suitable or preferred constructio'm For the forming part of each side of the purpose of clarity and to enable better appreciation oi the objects of my invention, I have deemed it advisable to show and describe a complete working example of a rubbing machine, which in this instance is of that type wherein the pad holders reciprocate in the same plane toward and from each other. Hence in the following description it will be borne in mind that the details of Construction referred to are simply for purposeof illustrating a single application of the motor. The body comprising a cylinder portion 21 and a slidcdnclosing portion 22, is preferably so shaped that the metal incorporated in its structure gives the machine the weight requisite to increase the effect of the abrasive means and facilitate the operation. Suitable means may be employed such as bolts 20, for securing the body portions rigidly together. The body portion 21 contains two cylinders 23 and 2% arranged in parallel relation and extending entirely through the body. Provisioiris made centrally between the ends of the body for the disposal of operating parts, by coring out this portion, as indicated, to form the chamber 25, which, it will be noted, intersects the central portion of the cylinders and in fact divides each cylinder into a double or opposedcylinder. Double-end pistons 26 and 27 slidable in the cylinders 23 and 2% respectively, are of the double acting type adaptedto take air pressure at both ends. The construction of the pistons and the means by which theyare pneumatically operated will be'described later on following a description of the slides and pad holders which are operated directly by the pistons.

Assuming now that the pistons are adapted to be reriprocated rapidly in opposite directions, l have made provision for connecting a burnishing pad or rubbing tool as directly as possible to each piston in order that the power may be applied in a most eflicient manner. in so doing, however. due regard must be had to the fact that because of the high speed at which the parts reciprocate, \vearin surfaces or guidcways of large area must provided for the padholder slides, and that it is also desirable The. portions 3], 35 and 34 and 3], 33 and 34 slidably engage in correspondingly shaped ways in the body portion of the tool and by reason of the substantial length of these surfaces or portions a considerable area of bearing surface is provided. Referring to Figs. 5 and 12, it will be noted that the lateral slide portion or wing 3-4 of the slide 29 is of a length nearly equal to the length of its respective piston, while the opposite lateral wing 33' is only about half the length of the wing 34.. It will also be noted that by arranging the slides 28 and 2!) so that they are in overlapping or telescoping rela tion, it is possible to obtain the relatively long bearing surface desired. In order to further guide the sides against lateral displacement the outer end of the wing portions 34 and 34: are provided with depending flanges 35 and 35 respectively which fits in correspondingly shaped grooves or ways in opposite sides of the body portion 22. In further reference to the telescoping relation of the slides 28 and 29 it will be noted that the long wing portions :34 and 84 are on opposite sides of the central slotway 32, and bear on their upper surfaces against the under surface of the cylinder body portion 21, and that the wing portions 33 and 33 of shorter length are disposed in a plane below that oi. the win; portions 34 and 34 and consequcntl y operating in spaced relation below the wing portions 34; and 34 of opposite slides. This will be observed particularly by refm-ence to Figure 7, which shows th wing portion 33 of the slide 29 disposed below the wing portion 34 of the slide 28. The body portion 22 which incloscs the slides just doscribcd may be formed at each side of two parts 3T and 38 suitably and rigidly secured together and shaped to provide the proper slidcways and inclosurr for the lateral wings of both slides.

The direct connection spoken of between the slides and their respective pistons is clearly illnstratcrl in Figs. T and 12 from which it will he observed that the slides a! and 29 are respectively provided with integral upstanding trunnions 39 or iii) littin ly engaged in apertures 41 and ll in their respective pistons centrally between the ends thereof. The central portion :3] or 3] of each slide is shaped beneath the machine body for attaclnncnt to the pad holder which carries th hurnishing pad or other abrasive means cniphiyed in the rubbing operation. From the foregoing it will he manifest that when air pressure is applied to opposite ends of the pistons (in amanner to be described hereinafter) they will be reciprocated rapidly in opposite dircctimis and will in turn directly reciprocate the padholder slides. The rubbing or polishing elements designated generally by 42 may be of any suitable construction and description is deemed unnecessary.

Coming now to the motor construction and operation, I have given considerable attention to this with the view to obviating.

certain defects in machines previously marketed. I have aimed primarily to secure simplicity and durability; and to this end I have concluded, after a long series or experimentation, that the various operating parts must be properly balanced and equalized so that there will be no vibration, that the forces be applied as directlyas' possible, that because of the higlr speed at which the parts operate maximum bearing surfaces are necessary, and that special provision must "be made for preventing any foreign matter member designated generally by character 43, shown in detail in Fig. 8, having a cross head .44 secured to a. central tlllIlIllOll or ipivotstud 4:") rotatable in the bore 46 of a ably secured to the body 21 by means of roca machine screws 48. The ends of the cross head 44 slidably co-operate with the pistons through the agency of slotted guides 49 formed integral with pivot pins 51 rotatable withinthe studs 39 aud t-39 of the slides28 and 29. To prevent interference between the equalizer arms and pistons the latter are cut awayas at 51'. They are also bored to reduce weight and momentum and are cut away centrally at their inner sides 52 to enable a proper mounting of the equalizer intern'iediate the pistons. From the foregoing it will be manifest that the pistonconnecting device, mounted to turn about an axis intermediate the cylindersand the ends thereof, embodies a diametrically disposed guideway which isv slidably associated. with apart moving with each piston. This device constitutes a very direct and simple means for maintaining the pistons in cooperative relation throughout their jrecipion. t

My invention also contemplates the actuation of a valve by and in SYflCllI'OIllSl'll with the pistons; and as a direct, practical and etlicient means to this end, I have arranged an oscillating valvein co-a'xial relation to the piston-connecting device and 'provided a connection whereb said device actuates the valve. The oscil atory valve illustrated in detail in Fig. 10 is adapted to be actuated directly by thenequalizing member 43 and consists of a 1 cylindrical portion 53 having a diametrical.slotway in its lower end which receives the equalizing member.

The valve isirevolublefin a bushing 54 fixed. in the body 21 in axial alignment with the outl y mentioned.

equalizer and is provided-with an annular :head 55 seated on top of the bushing to take the heavydown thrust imposed by the air pressure. A steel washer 56 may be interposed between the bushing 54 and the head 55 of the valve and serve effectually as a wear seat therefor. Air under pressure is supplied to the machine from a suitable source as. through a handle 57 detachably secured to the body 21 in axial alignment with the valve and having an air passage 58 communicating therewith. Removal of the handle 57 gives access to the valve chamber and permits easy removal of the valve. The air passes downwardly through the passages 59 and 61 (Fig. 10) in the valve and is adapted to enter the passages 62, 63, 64 and 65 at proper intervals as determined by oscillation of the valve for moving the pistons back and forth. It will be noted that the passages 59 and 61 in the valve intersect its periphery at diametrically opposite points and. are adapted to register with the ports in the bushing which communicate with the air inlet passages 62 to 65 inclusive. As indicated in Figs. 2 and 14, theair inlet passages communicate with the ends of the cylinders. The valve port, coplanar with the air intake passages and ports, include exhaust ports 66 and 67 adapted to register at proper intervals with both the ports of the intake passages mentioned and the exhaust passages 68 and 69 disposed intermediate the air intake passages. These exhaust passages connect, as shown in Figs. 1 and 15, with passages 71 formed in end plates 72 whi :h entirely cover the ends oi: the body portions 21 and 22and consequently close the ends of the cylinders. The end plates may be suitably secured to the body bymachine screws 73 or the like passing through openings 73. I The upright passages Tlin the end plates comnumicate at their lower ends throng-l1 openings 74- (Fig. 3) with openings. 75 arranged from end to end in the body portions 38 in close proximity toand blanking both sides of the central slotwav These openings are restricted at their under-sides to provide inarrow months '76 coextensive with the length of the slot-way 32 and through which the exhaust air will be forced downwardly for the purpose of preventing foreign matter ctrom entering the slotway and working up wardly into the operating mechanism.

Referring again to the valve it will be noted, viewing Figs. 4 and 16, that there isprovision made in the connection between the valve and equalizing member for a certain amount of lost motion between these parts, that is, the equalizing member and consequently the pistons maybe moved apredetermined distance independently of any movement oi the valvei or a purpose pres- This is acconi ilished in the present instance by cutting away opposite ends otthe slot in the valve, as shown at 53'. A splash guard 77 underlying the machine throughout the length thereof, is secured at its ends to the end plates 72. This guard prevents water and pumice from splashing upwardly into the slotway 32 and serves to deflect the exhaust air outwardly away from the active working faces of the rubbing elements. 1

The operation of my improved rubbing and burnishing machine will now be described. In all of the assembled views in .the drawings, except Figs. 15 and 16, the

parts are shown in neutral position, that is, one in which. the air under pressure admitted to the machine will not actuate the pistons until the valve has been moved slightly beyond its dead center position. In the neutral position it will be noted, that the pistons 26 and 27 are both centrally disposed in their respective cylinders, as shown in Fig. 4, and that the valve as shown in Fig. 14:, precludes the air pressure from entering the cylinders. Upon moving the slides in either direction the valve will be oscillated through the agency of the member 43 as described above, so that the passages 59 and (ii of the valve will register with either the cylinder air passages 62 and or the passages 63 and G4. dependent upon the direction in which the valve is oscillated. As shown in Fig. 15, the valve has been oscillated in a clockwise direction, thus connecting the air supply with the passages 62 and (35 and consequently admitting the air to the lower left hand piston and upper right hand piston shown in F i g. 16, whereupon the pistons will be forced by the air pressure to the opposite ends of the cylinders. The piston action is very rapid and in order that the stroke may be accomplished before the valve reverses the air supply to the opposite end of the cylinders to effect the reverse piston action, a lost motion is provided between the valve and the member 43. This permits the pisstons to more independently of the valve and acquire sufiicicnt momentum to carry them to the end of their stroke before the valve is oscillated to admit the reverse air supply. This action will be. plainly seen by reference to Fig. 16 from which it will be. noted that the pistons may more nearly half the length of their stroke before the alve will be oscillated by the member 51in a counter-cl nkwise direction. By changing the amount of lost motion between the valve and member 43. the length of the piston stroke may be varied. While the cylinders are taking air through the intake passages 62 and 65 as just mentioned, the opposed supply passages 63 and 64- will be connected thru the valve ports 66 and 67 with the exhaust passages 68 and 69 respectively, so that as the pistons are driven in one direction the exhaust air of the opposed cylinders will be simultaneously expelled from their respective cylinders and forced down through the passages 71, and out of the long narrow months 76 at the underside of the machine. The valve action just described takes place automatically, that is, reverses automatically. due to the alternating action of the opposed cylinders. As a consequence of this action the pistons will reciprocate very rapidly at a speed dependent. of course, on the air pressure and upon the resistance to the rubbing tools due to the nature of the work being performed. In view of the rapidity of this operation the exhaust air will be substantially continuous and consequently, will be forced into the openings from both ends and discharged downwardly through the narrow months 76 throughout the length of the machine. This downwardly discharging exhaust air will strike the to of the splash guard 77 and will be deflector laterally with such force and continuity as to prevent any foreign particles arising, or splashing up during the rubbing action from entering the slotway and consequently working up intothe operating parts of the mechanism. By utilizing the exhaust air in this manner a very effectual means is provided for keepingthe operating mechanism clean and in good working condition; and in this regard it will be especially noted that the exhaust air is not passed through the operating mechanism. suchas through the slide bearings, etc., but is conveyed in passages entirely separate from these and is then applied at the desired points of use. Consequently, the bearing surfaces are not subjected to the blast of exhaust air and there is no danger of foreign particles being carried through the slotway to said surfaces, with consequent injury thereto.

From the foregoing, it will be observed that I have provided a motor construction peculiarly and advantageously adapted for reciprocating a pair of rubbing or polishing devices, especially in that the few parts are equally balanced and are very compactly ar ranged and the forces are. transmitted inost directly and efficiently. Thus, vibration is eliminated and themachine is smooth-running, regardless of the high speed atwhieh it. operates; consequently the wear is reduced to a minimum. The arrangement also promot-es economy in manufacture and enables comparatively quick and easy assembling and disassembling. It will also be manifest that neither the construction, number, nor arrangement of the pad-holder slides or de vices are material to the present invention,

which relates primarily tothe motor.

It is believed that the foregoing conveys a clear understanding to those familiar with this art, of the objects prefaced above, and while I have illustrated but a single working till IUD

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ally spaced cylinders, a in each cylinder, a 'mem er pivoted intermediate the pistons and. between the ends rect engagement with said pistons intermediatetheir ends for actuating said valve.

2. In a machine of the character disclosed, the combination of a pair of cylinders in parallel laterally spaced relation, a doubleend piston reciprocable in each cylinder, means pivotal about an :axis intermediate and between the ends ofthepistons and connected with the latter for maintaining them in co-operative relation during (and tin-oughout their reciprocation in opposite directions, and valve mechanism operated by movement of said pivotal means for controlling: the delivery of fluid under a pressure to the cylinders.

3. In a machine of the character disclosed, the combinationof a pair of parallellateriston reciprocable thereof and having ;a slidable connection with each piston, whereby to maintain the pistons in co-operative relation throughout their reciprocation, and a valve actuated by said pivoted member for controlling the delivery of fiuidunder pressure-to the cyl- 4. In a a machine of the character disclosed, the combination of a body formed with a pair of cylinders, pistons therefor, an :oscillatory valve adaptedto govern pressure fluid to both cylinders forreciprocating the pistons in opposite directions, passages between :said .valve and said cylinders, and a single means coaxialiwith said valve for operating the latter and operable by the reciprocation of said pistons, said last mentioned means being enclosed within said body and having alost motion connection with said "valve. I

5. In a machine of the character described,

the combination of a bodyhaving a pair of parallel laterally 'sphoedcylinders and havmg an opening in its top wall between and intermediate the ends of said cylinders, two pistons one of which is mounted ineach cylinder, an oscillatory valve member-in said opening for controlling the pressure fluid to said cylinders, said valve member being freely removable from said opening, and an upstanding handle detachably mounted on saidbody, said handle closing said opening and having a conduit through which the fluid under pressure .isdirccted to said valve member.

6. In a machine of the character disclosed, thecombination of a pair rdparallcl laterally spaced cylinders, a double-end piston in each cylinder, moans providing a connection between the pistons whereby to maintain them in cooperative relation tln'oughout their reciprocation, said means being pivotal about nnaxis intermediate and between the ends of the pistons and having an oscillatory connection with each piston about a fixed axis thereon, and a valve actuated by oscillation of said means for controlling the de livery of fluid under pressure tothepistons for reciprocating them in opposite. directions. 7. In a machine of the character disclosed, the combination of a pair of cylinders, a double-end piston reciprocnble in each cylinder,a member pivotal about an axis betweenand intermediate the endsotthe pistons and having a diametrically disposed guide, anemia oncach piston slidably associated with said guide whereby to maintain the pistons in co-operativerelation throughout their reciprocation in opposite directions, an oscillatory valve coaxial with said memher and actuated by oscillation thereot, and passages between said valve and the cylindersavhereby the valve controls the delivery ottluid under pressuretothe cylinders for reci mncating the pistons in opposite dircctions. i y a 8. In a machine oi the character disclosed, the icombmation or a pair ,ot cylinders. a

donble-end piston in each cylinder, at ,pivotal member operatmg between the pistons to maintain them in co-operative relation throughout their reciprocation, and a valve having a lost motionconnection \V-ltlhfllld actuated by said member for governing the delivery of fluid under pressln-e to thecylinders.

9. ,In amachine of -the character disclosed, thecombination of a pair of cylinders, a piston in each cylinder, amember operable between the pistons for nmintainingthem in co-operativerelationthroughout their re ciprocation, and an oscillatory valve having a lost motion connection with said member and adapted to be actuated thereby for governing thcdelivcry of fluidnnder pres sure to the cylinders.

10. The combination of a closed body having a plurality of cylinders, a pair otpistons in said cylinders, a member having a central bearing hub pivotally mounted in said body for movement in a single plane and having a cross head whose ends are slidab'ly associated with the pistons whereby to maintain them in (to-operative relation 1 throughout their reciprocation,and a valve actuated by movement of said pistons for controlling the delivery of fluid under pressure to the cylinders.

11. The combination of a body havin a pair of cylinders, a piston in each cylinc er, a member having a central bearing hub pivotally mounted between the pistons and having a cross head whose ends are slidably associated with the pistons whereby to maintain them in co-operative relation throughout their reciprocation, and an oscillatory valve co-axial with said piston-connected member and actuated thereby for controlling the delivery of fluid under pressure to the cylinders.

12.. The combination of a body having a pair of cylinders, a piston in each cyinder, a member having a central bearing hub pivotally mounted between the cylinders and having a cross head whose ends are slidably associated with the pistons whereby to maintain them in co-operative relation throughout their reciprocation, an oscillatory valve co-axial with said member and having a bifurcated end for the reception thereof, and passages providing communication between the valve and the cylinders.

13. The combination of a body having a pair of cylinders, a piston in each cylinder, a slide adapted to he reciprocated by each piston and having an upstanding cylindrical partfitting in a bearing in its respective piston, a bearing pin co-axially mounted in each upstanding part and having a diametrical guideway therein, a member pivotally mounted between the pistons and having diametrically opposed parts slidably fitting in the guideways in said pins, thereby establishing a connection between the pistons serving to maintain them in co-operative relation throughout their reciprocation, and valve means controlling the admission of pressure fluid to and from said cylinders to reciprocate the pistons.

14. The combination of a pair of parallel laterally spaced cylinders, a double-endpiston in each cylinder, devices adapted to be operated by the pistons, means movable about an axis between the pistons and the ends thereof and connected respectively with the pistons for maintaining them in co-operative relation throughout their reciprocation, and valve mechanism actuated by said means for governing the delivery of fluid under pressure to the cylinders for the purpose of reciprocating the pistons in opposite directions.

15. In a machine of the character disclosed, the combination of a pair of doubleacting pistons adapted to reciprocate in opposite directions, oscillatory means centrally in co-operative relation throughout their reciprocation, and means actuated by said first mentioned means for controlling fluid pressure to the pistons for reciprocating the latter.

16. In a machine of the character dis closed, in combination, a body having a pair of laterally spaced cylinders, a piston reciprocablcin each cylinder. an oscillatory valve enclosed within said body and movable about an axis intermcaliate and between the ends of saidpistons, inlet passages in said body portion above said cylinders adapted to connect said valve with the outer cndsol" both cylinders. exhaust passages in said body portion above said cylinders adapted to connect said valve with the exhaust, a pressure fluid supply passage above said valve, and means in said body, and coaxial with said valve positioned between said pistons for actuating said valve to alternately connect said inlet passages and said exhaust passages alternately to opposite ends of: said cylinders. i

17. In a machine of the character disclosed. in combination, a pair of laterally spaced cylinders, a double end piston reciprocable in each cylinder, a member pivotal about an axis intermediate the ends of and between said istons and having a diametrically disposed guide, said guide having a sliding and rotary connection with each piston, an oscillatory valve coaxial with said inembe and actuated by movement thereof, and passages between said valve and said cylinders whereby said valve controls the delivery of fluidunder pressure to said cylinders for reciprocating the pistons in opposite directions.

18. A machine of the character disclosed having, in combination, a body having a closed chamber, means extending through said chamber and being formed with a bore intermediate its ends, a pair of spaced cylinders, two pistons one of which is reciprocable in each cylinder, a pivotal member having a central pivot stud bearing in said bore and having a sliding and pivotal connection with each piston to maintain said pistons in cooperative relation throughout their reciprocation in opposite directions, and valve means actuated upon movement of said pistons to control the delivery of fluid under pressure to said cylinders.

19. A machine of the character disclosed having, in combination, a pair of laterally spaced cylinders, a piston reciprocable in each cylinder, :1 member having a central bearing hub pivotallymounted between the cylinders and having a lateral portion constitnting a guide, means carried by said pistons for slidably engaging said guide and oscillating said member upon a reciprocation of said pistons, and an oscillatory valve coaxial with respect to said member and operable by oscillation of the latter to control the admission of fluid pressure to said cylinders.

20. A machine of the character disclosed comprising, in combination, a body portion having parallel laterally spaced cylinders, pistons mounted in said cylinders for reciprocation in opposite directions, a valve member positioned Within said body between said cylinders for controlling the admission of fluid pressure to the latter, means supported in said body portion and engaging said valve member and said pistons, said means acting to maintain the pistons in cooperative relation. throughout their reciprocation and to actuate said valve member near the end of the stroke of said pistons, and means for supplying fluid pressure to said valve member.

21. In a machine of the class described, in

combination, a closed body formed with cylinders, pistons movably mounted in said cylinders, said body being formed with a central chamber and a bore opening into In a machine of the character de-' scribed, in combination, a closed cylinder body having a closed central chamber, a pair of pistons movably mounted in said cylinder body, pins carried by said pistons, and an equalizing member rotatably mounted 111 sald chamber and slidably and rotatably as sociated with each of said pins to cause said pistons to move in synchromsm.

SWAN F. ANDERSON.

CERTIFICATE 0F CORRECTION.

Patent No. 1,677,112. Granted July 10, 1928, to

SWAN F. ANDERSON.

It is hereby certified that. errorappears in the printed specification of the abovenumbered patent requiring correction as follows: Page 3, line 92, after the word "communicate" insert the words; "through passage 62363 64' and 65' respectively"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 7th day of August, A. D. 1928.

M. J. Moore;

Acting Commissioner of Patents. 

